Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$51.25	12.382%	$57.5958	$57.60	$57.60	$57.60
Purchase #2	$174.94	8.863%	$190.4449	$190.44	$190.45	$190.40
Purchase #3	$76.77	13.165%	$86.8768	$86.88	$86.90	$86.90
Purchase #4	$212.26	6.294%	$225.6196	$225.62	$225.60	$225.60
Purchase #5	$146.71	3.310%	$151.5661	$151.57	$151.55	$151.60
Purchase #6	$102.92	12.788%	$116.0814	$116.08	$116.10	$116.10
Purchase #7	$171.51	10.827%	$190.0794	$190.08	$190.10	$190.10
7 purchase totals =	$936.36		$1,018.2640	$1,018.27	$1,018.30	$1,018.30